It is easy to be wise after the event. 事後諸葛亮人人會做。
Why criticize other people when you once knew no better yourself? 你也不過是事後諸葛亮,幹嗎批評人家?
牛津高階第八版
美國韋氏詞典
Dictionary.com
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維基百科 (自由的百科全書)